Passive Turbulance Control Product for Minimizing Drag and Its Method of Manufacture

ABSTRACT

A method of manufacturing a surface that will reduce fluid flow drag over exposed surfaces of aerodynamic or hydrodynamic structures. The surface shall define a plurality of dimples. The dimples might not be aligned. Adjacent dimples might not have the same diameter.

FIELD OF THE INVENTION

The present invention relates to the art of reducing fluid flow dragover aerodynamic or hydrodynamic surfaces, e.g. watercrafts, airplanes,automobiles, airfoils, rudders, propellers, rockets to name a few. Theinventor has developed a method of placing a dimple pattern to all ofthe exposed surfaces that would be in contact with the fluid flow,thereby reducing the fluid flow drag. The dimple pattern would besimilar to the pattern found on existing golf balls. The dimple patterncould be applied to the surfaces prefabrication or post fabrication. Thedimple pattern would be stamped on to prefabricated surfaces. Toexisting surfaces, a dimple pattern film would be applied to thesurfaces.

BACKGROUND

There is a need to reduce the drag, the combined effects of frictiondrag and pressure drag, felt by bodies when passing through a fluidflow. When the drag effect felt by a body is reduced, the energynecessary to have the fluid flow is decreased exponentially hence inmost instances the fuel consumption is reduced. For example, it has beenestimated that a one percent reduction in drag across the leading edgeof a wing of one BOING 727 jet airliner would reduce the fuelconsumption by more than 20,000 gallons per year. See AutomotiveEngineering, February, 1982, pp. 73.

Reducing the drag felt across all the exposed surfaces of a body, notjust the leading edge of a wing, will also reduce fuel consumption whena body is passed through a fluid flow. For example, it is desirable toreduce the drag caused by water flowing past the hull of a boat, airflowing past a moving automobile or air flowing past the blades of awindmill fan, airfoil, fan, rotor, stator, inlet, etc. The inventor ofthe present invention realized that if he could provide a method ofreducing the drag effect felt by all exposed surfaces of a body, that hewould reduce the energy required to make the body travel through thefluid. The present invention is directed to providing a commerciallyviable solution for reducing the drag effect felt by all the exposedsurfaces of a body when the body passes through a fluid flow.

Friction drag and pressure drag are persistent problems in aerodynamicand other types of fluid flow design. Friction drag results primarilyfrom the force of friction between a surface such as a wing or afuselage section and the air or other fluid found within the boundarylayer adjacent to that surface. When a body passes through a laminarfluid flow, the effect of friction drag is relatively small. However,when a body passes through a turbulent fluid flow, the frictional dragforce is typically greater when compared to a laminar flow. With respectto modern aircraft, the frictional drag component can account for fiftypercent or more of the total drag force experienced by such aircraft.Similarly, other aerodynamic or hydrodynamic structures such as awatercraft, automobile, airfoil, rudder, propellers, rockets or the likemay experience large frictional drag forces due to turbulent flowpassing over their external surfaces.

A second type of drag occurs when a fluid flow passes over anaerodynamic or hydrodynamic surface, hereinafter either surface shall bereferred to as “surface,” and the fluid flow separates from the surface.The separation creates low pressure pockets behind the surface. Suchfluid flow separation might be caused when the surface interacts withthe fluid flow at a high angle of incidence or “angle of attack.” Theresulting low pressure pocket creates a retarding force and is commonlyreferred to as pressure drag.

An energized or turbulent flow is less likely to become separated from asurface than a non-energized or laminar flow. Thus, one method ofreducing pressure drag is to artificially convert or “trip” the laminarfluid flow over the surface to a turbulent flow. The energy within theturbulent boundary layer helps to maintain the flow attached to thesurface, thereby reducing or delaying flow separation until a higherangle of attack so that a reduction in the total amount of pressure dragis achieved.

Many prior methods have been used to reduce both friction and pressuredrag. With respect to pressure drag, some of these methods includeadding structures to the leading edge of surfaces. Such structures mayinclude rough strips extending span wise along the leading edge of thesurface or a plurality of vortex generators spaced along the leadingedge. These structures extend into the relatively thin laminar boundarylayer to disrupt the laminar flow, thereby prematurely tripping the flowto a turbulent state and energizing the boundary layer so that the flowis less likely to separate from the surface. While these and othersimilar structures may successfully reduce the pressure drag associatedwith flow separation, they do not address the resultant increase infriction drag caused by the larger proportion of turbulent flow withinthe boundary layer.

With respect to friction drag, a turbulent boundary layer has a greatervelocity gradient than a laminar boundary layer, and the greatervelocity gradient, combined with the inherent instability within theturbulent boundary layer, tends to transfer a relatively high amount ofmomentum from the boundary layer to the aerodynamic surface. Prior meansfor reducing friction drag have included both passive and activetechniques for reducing the instability or the momentum transfer withinthe turbulent boundary layer. Examples of the passive control meansinclude rivets formed on the surface and application of films andcoating systems with grooves and rivets aligned in the stream wisedirection of the fluid flow over the surface, the stream wise groovesformed by the rivets attempt to redirect the stream wise fluid flowwithin the boundary layer away from the surface, thereby reducing themomentum transfer between the boundary layer and the surface. However,while such passive devices have demonstrated that they are capable ofreducing friction drag, the net effects of such devices are lessened dueto offsetting drag increases in other areas. For example, while rivetsmay decrease the effect of friction drag, they also increase the wettedsurface area of the surface so that the total amount of friction drag isnot dramatically decreased. Additionally, the parameters of the rivetsare not easily changed once they are optimized for a particular flightcondition. The passive devices described above contribute extra form ordevice drag to the total drag of the surface. One example of an activeform of friction drag control is a suction system in which a pattern offine holes is formed in the aerodynamic surface. Suction is applied tothe holes to create a pressure gradient that suppresses instabilitygrowth within the turbulent boundary layer. However, the obviousdrawbacks of such a system include its cost, ongoing maintenance and itssusceptibility to adverse weather conditions.

Many solutions have been proposed for mechanically altering fluid flowover flow control surfaces. For example, the utilization of variousdevices to direct air into ducts exiting the trailing edges of the flowcontrol surfaces. See, for example, U.S. Pat. Nos. 2,742,247; 2,925,231;3,117,751; 3,521,837; 4,114,836; 4,258,889; and 4,296,899. U.S. Pat. No.4,434,957 suggests the use of a corrugated fluid control surface. Thecorrugations that extend transversely into the direction of the fluidflow temporarily retain vortices formed in the fluid flow on the flowcontrol surface, and aid in regulating the passage of the fluid flowacross the surface. U.S. Pat. No. 4,455,045 proposes the use of one ormore 3-sided submerged channels in the flow control surface. Eachchannel includes two divergent walls that form a generally V-shaped rampthat is sloped downward so that each channel widens and deepens towardthe downstream flow of the fluid flow. Such channels are V-shaped in aplane and are generally parallel to the flow control surface. Thechannels are intricate and are most effective when provided in a serialcascade and wherein the last channel in the cascade ends at the trailingedge of the flow control surface. The above inventions are expensive todevelop, time consuming to employ and do not provide a solution forreducing the drag felt by a body's exposed surface when the body passesthrough a fluid flow.

The use of smooth surface coatings on airplane skins have also beensuggested. See Automotive Engineering, February, 1982, pp. 73-78. Thearticle reported that liquid polymeric coatings and adhesively backedfilms applied to flow control surfaces, in order to maintain a smoothand protected surface for reducing drag, performed poorly and wereunsuitable for areas of high erosion such as wing and tail leading edgesand nacelle inlets. U.S. Pat. Nos. 4,872,484 and 4,974,633 describesystems for affecting the fluid flow relative to an object. The patentsdisclose having a plurality of surface deviations disposed on thesurface of an object in which the deviations are grouped into at leastone set and the sets are arranged into at least one predeterminedpattern. The patents do not address having the deviations covering thetotality of the exposed surfaces of a body that passes through a fluidflow.

U.S. Pat. No. 5,069,403 discloses a practical technique forsignificantly reducing drag only across the flow control surfaces giventhat in general, at these surfaces, the fluid trajectory isperpendicular to the film and the patterns stated therein are aligned inthe stream wise direction to the fluid flow. The invention comprises ofa conformable sheet material that employs a pattern surface to reducedrag. The material is used on certain areas of aerodynamic orhydrodynamic structures. The material is not used to cover all exposedareas of a body passing through a fluid flow.

An article written in 1992 entitled “Suppression of Turbulence inWall-Bounded Flows by High-Frequency Span Wise Oscillations,” Lung etal. utilized computational fluid dynamics simulations to determinewhether a reduction in turbulence-induced drag could be realized in asimulated bounded channel flow by rapidly oscillating one of the channelwalls in a span wise direction (orthogonal to the direction of thesimulated free stream channel flow). The article notes that theturbulent bursting process was suppressed and significant reductions inthe calculated turbulent drag force were realized. However, Lung et al.offered no explanation or suggestion of how the span wise oscillationscould be achieved outside the purely computational realm. U.S. Pat. No.5,901,928 discloses an active turbulence control technique for dragreduction that is based on the active generation of bending waves. Thetechnique is limited in its application: applicable only to surfaces onwhich fluid trajectory is perpendicular to the wave oscillationgenerator. Because such application can only be utilized on certainareas of an aerodynamic or hydrodynamic structures such as a watercraft,airplane, automobile, airfoil, rudder, propellers, rockets or the like;therefore limiting the practical application and not significantlyimproving the overall performance of the structure.

An object of the present invention is to reduce drag over all exposedsurfaces of a body when the body passes through a fluid flow.

Another object of the present invention is to reduce the energy requiredfor a body to travel through a fluid flow.

Other objects of the invention will become apparent in view of thefollowing description taken in connection with the accompanyingdrawings.

SUMMARY

The object of the present invention is to provide a surface that willreduce the drag and thereby reduce the energy required for a body totravel through a fluid flow by stamping an existing surface with adimple pattern design similar to those found in golf balls or bycovering the surface with a film having a similar a dimple patterndesign. The present invention may be used on the following bodies:watercrafts, aircrafts, automobiles, airfoils, rudders, propellers,rockets or any other body that may be in contact with a fluid flow.

When either stamping the exposed surfaces with the dimple pattern designor when covering the exposed surfaces with the dimple pattern designfilm, the dimple pattern design will reduce the drag over the exposedsurfaces by energizing the boundary layer between the fluid and thesurface, thereby enhancing the turbulent process by disrupting thelaminar flow and reducing the transfer of momentum between the turbulentflow and the surface.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and drawings where:

FIG. 1 illustrates a spherical square having a dimple pattern for a golfball that is more fully described in FIG. 4 of U.S. Pat. No. 4,960,281;

FIG. 2 illustrates a spherical equilateral triangle having a dimplepattern for a golf ball that is more fully described in FIG. 4 of U.S.Pat. No. 4,960,281;

FIG. 3 illustrates another spherical square having a dimple pattern fora golf ball that is more fully described in FIG. 4 of U.S. Pat. No.4,960,281;

FIG. 4 illustrates a preferred spherical square having a dimple patternfor a golf ball that is more fully described in FIG. 4 of U.S. Pat. No.4,960,281;

FIG. 5 illustrates a preferred spherical square having a dimple patternfor a golf ball that is more fully described in FIG. 4 of U.S. Pat. No.4,960,281;

FIGS. 6A-6B show cross sectional views of how fluid flow flows acrosssections of an airfoil, one figure uses the first embodiment of thepresent invention and the other does not;

FIG. 7 illustrates a perspective view of an airfoil utilizing the firstembodiment of the present invention;

FIG. 8 illustrates a cross sectional view of the airfoil utilizing thefirst embodiment of the present invention;

FIGS. 9 and 10A illustrate a top view and greatly enlarged crosssectional view of the second embodiment of the present invention as aconformable dimple pattern film.

FIG. 10B illustrates a side view of the second embodiment of the presentinvention as a conformable dimple pattern film and its edge finish.

FIG. 11 illustrates a perspective view of how the second embodiment ofthe present invention is applied as a film layer to exposed surfaces ofan aircraft's fuselage and the fluid flow lines showing non-linearflows.

FIG. 12 illustrates a perspective view of the second embodiment of thepresent invention applied to exposed surfaces of a commercial jetaircraft's fuselage and the fluid flow lines showing non-linear flow.

DESCRIPTION

A method of manufacturing a surface that will reduce fluid flow dragover exposed surfaces of aerodynamic or hydrodynamic structures. Thesurface is manufactured by providing a surface that will be used tofabricate exposed surfaces of aerodynamic or hydrodynamic structures andapplying a dimple pattern design, similar to those found in golf balls,to the surface.

As shown in FIGS. 1-7, the present invention is directed to a method ofmanufacturing a surface that will be used to reduce fluid flow drag overexposed surfaces of aerodynamic or hydrodynamic structures. The surfaceis manufactured by providing a surface that will be used to fabricateexposed surfaces of aerodynamic or hydrodynamic structures and applyinga dimple pattern design, similar to those found in golf balls, to thesurface. The dimple pattern design is more fully described in U.S. Pat.No. 4,960,281. As shown in FIGS. 1-5, the dimple pattern designs stampedon the exposed surfaces are not linearly aligned. In a preferredembodiment, the dimple pattern designs will be composed of dimples andadjacent dimples shall have different diameters. The dimple patterndesigns will be applied to exposed surfaces of aerodynamic orhydrodynamic structures that will be in contact with a fluid flow, e.g.watercrafts, aircrafts, automobiles, airfoils 4, rudders, propellers,rockets or any other body that may be in contact with a fluid flow.Methods of stamping surfaces are known in the art of stamping and shallnot be described herein.

The dimple pattern designs of FIGS. 1-5 can be stamped onto curved orflat exposed surfaces. The novelty of the invention is applying thedimple pattern design to exposed surfaces of aerodynamic or hydrodynamicstructures that will be in contact with fluid flows.

FIGS. 7-12 show a second embodiment of the present invention. In thesecond embodiment, a film defining a dimple pattern design ispermanently attached to an exposed surface of aerodynamic orhydrodynamic structures. The film is a conforming film that defines adimple pattern design that is capable of withstanding intense fluidflows. The conforming film having a dimple patterned surface comprisedof a plurality of dimples. In a further embodiment of the presentinvention, the dimples will not be linearly aligned. In anotherembodiment, adjacent dimples shall have different diameters. A number ofmaterials can be used to make the film. While the exact material used toprovide the article of the invention is not critical, it is noted thatcertain materials may be better suited for certain environments. Forexample, when the surfaces are exposed to high temperatures, thermosetflexible materials might be preferable to thermoplastic materials. Inwater environments, water-resistant materials might be preferable towater sensitive materials.

It is foreseen that the film used in the second embodiment of thepresent invention may have an inherently adhesive side, the side wouldbe permanently attached to the surfaces. Such film might be eitherpassively adhesive or actively adhesive. In the former case, theadhesive might be activated by applying solvents, heat, pressure, or thelike to the adhesive side prior to applying the film to the surface. Inthe latter case, such activation would not be necessary. In the eventthat a separate layer of adhesive is employed, the adhesive may beselected from a wide variety of materials such as heat activatedadhesives, solvent (organic or inorganic) activated adhesives, orpressure sensitive adhesives. These adhesives preferably are compatiblewith the carrier to which they are applied and are resistant to water,oil, hydraulic fluids and the like. Furthermore, the separate adhesivelayer preferably does not separate from the carrier during use. See U.S.Pat. No. 5,069,403.

An advantage of the present invention is that it reduces drag over allexposed surfaces of a body when the body passes through a fluid flow.

Another advantage of the present invention is that it reduces the energyrequired for a body to travel through a fluid flow.

While we have shown and described the embodiment in accordance with thepresent invention, it should be clear to those skilled in the art thatfurther embodiments may be made without departing from the scope of thepresent invention.

1. A method of manufacturing a surface that will reduce fluid flow dragover exposed surfaces of aerodynamic or hydrodynamic structurescomprising steps of: providing a surface that will be used to fabricateexposed surfaces of aerodynamic or hydrodynamic structures; and applyinga dimple pattern design, similar to those found in golf balls, to thesurface.
 2. The method of claim 1, wherein the dimple pattern design isapplied by stamping the surface with the dimple pattern design when thesurfaces are manufactured.
 3. The method of claim 2, wherein the dimplepattern design is composed of dimples and the dimples are not linearlyaligned.
 4. The method of claim 3, wherein the dimples will havedifferent diameters when placed adjacent to each other.
 5. The method ofclaim 1, wherein the dimple pattern design is applied to the surface byapplying a conforming film, the conforming film having a dimplepatterned surface comprised of a plurality of dimples.
 6. The method ofclaim 5, wherein the dimples are not linearly aligned.
 7. The method ofclaim 6, wherein adjacent dimples shall have different diameters.